1. Field of the Invention
The invention pertains to a sensor arrangement for monitoring an area of the space in front of at least one motorized wing of a door. Transmitters emit radiation, whereas receivers react to the differing intensities at which this radiation is reflected and thus generate a signal which controls the drive of the door.
2. Description of the Related Art
U.S. Pat. No. 4,467,251 describes in detail a photoelectric device, which can be installed to serve as a sensor device in, for example, the bar handle of a door wing in order to monitor the space in front of the wing. The sensor arrangement has a housing, extending in the form of a bar across the entire width of the wing; a large number of beam-emitting and beam-sensitive sensors are arranged next to each other in linear fashion in this housing. The beams, preferably light beams, are emitted in an approximately horizontal direction, so that, when the power of the emitted light is adjusted properly and the sensitivity of the elements which receive the light is adjusted properly, an area of the space near the wing extending approximately at the level of the bar handle is monitored. This arrangement suffers from the disadvantage that the monitored spatial area does not extend all the way to the floor, which means that small children, for example, can creep under the monitored space and would be in danger of being hit by the wing of the door, if it were to open.
The previously known idea of combining transmitters and receivers to form a compact, bar-shaped module is also disadvantageous in that the functionality of the individual sensors cannot be tested. A defective module can be determined only on the basis of a deviation of parameters of the entire module from a reference value. An evaluation of this type, however, is unsatisfactory, because the result obtained does not indicate the exact source of the defect, which could even be caused by external influences. It is impossible to know which individual sensor, if any, is defective. It is extremely important to have this knowledge, however, because these types of units have important, safety-relevant functions, and a malfunction or a complete failure of certain individual sensors can in the extreme case result in injury to the person passing through the door system or can have even more far-reaching consequences in an emergency situation such as a fire.